A091898 Numbers that change from composite to prime or vice versa for at least one permutation of their digits.

14, 16, 19, 20, 23, 29, 30, 32, 34, 35, 38, 41, 43, 47, 50, 53, 59, 61, 67, 70, 74, 76, 83, 89, 91, 92, 95, 98, 101, 103, 104, 106, 107, 109, 110, 112, 115, 118, 119, 121, 124, 125, 127, 128, 130, 133, 134, 136, 137, 139, 140, 142, 143, 145, 146, 149, 151, 152, 154

Offset: 1

Author

Rick L. Shepherd, Feb 09 2004

Keywords

• base
• nonn

Comments

This is actually a subsequence of the complement of A091897, the union of A003459 and A067012: This sequence contains no powers of 10 (A011557) as 1 is not prime.

Clearly also no repdigit number (A010785) is a term nor is any number with only even digits (except for 20,200,2000,...) nor is any number divisible by 3 (except for 30,300,3000,...). Among other primes, this sequence does include all primes p > 5 which contain at least one of the digits 0,2,4,5,6,8.

Examples

			14=2*7 (composite) is a term as a permutation of its digits gives 41 (prime).
Hence 41 is also a term. 19 (prime) is a term as 91=7*13 (composite). Thus 91
is also a term. 130=2*5*13 (composite) is a term (even though the permutation
310=2*5*31 is also composite) because another permutation (0)13 (prime) exists
(dropping the leading 0). 13, however, is not a term as 31 is also prime (13
and 31 are members of A003459).
		

Crossrefs

Cf. A003459 (absolute primes), A067012 ('absolute composites'), A091897 (union of A003459 and A067012), A010785 (repdigit numbers).